1. Field of the Invention
This invention relates generally to the attachment of metal elements to a synthetic resin substrate or body, and more particularly is directed to an improved method and apparatus for securely anchoring in the synthetic resin substrate or body metal elements, such as, guide pins, shafts and the like, which are to project from a surface of the body.
2. Description of the Prior Art
There are many occasions when it is necessary to provide a synthetic resin body or substrate, for example, a molded resin chassis or casing of a tape recorder or the like, with a plurality of metal elements, such as, guide pins, shafts and the like, which are to be anchored or embedded in the synthetic resin body and to project from a surface of the latter.
In an existing method for thus securing the metal elements to a synthetic resin body, each of the metal elements has a mounting portion at one end preferably formed with a knurled or roughened surface and with a cross-sectional area larger than that of a hole provided therefor in the body. A guide jig is placed against the surface of the body from which the metal elements are to project and is provided with guide bores aligned with the holes in the resin body and dimensioned to slidably receive the respective metal elements which are inserted with their mounting portions directed toward the resin body. When thus positioned by the jig, the metal elements are pressed axially in the direction into the respective holes and simultaneously have ultrasonic energy imparted thereto, for example, by respective tips extending from an ultrasonic horn and urged against the ends of the metal elements remote from their mounting portions. The ultrasonic energy thus transmitted to the metal elements is focused or localized at the areas of contact of the knurled surfaces of the mounting portions with the surfaces of the holes in the resin body so that the surfaces of the holes are fused to permit the mounting portions to enter such holes. Upon the full insertion of the mounting portions in the respective holes of the body, the application of ultrasonic energy is halted with the result that the previously fused synthetic resin sets or hardens about the knurled surfaces of the mounting portions for securely retaining the latter in the resin body with the respective mounting elements projecting therefrom within the guide bores of the jig.
The foregoing method is disadvantageous in that, in spite of the use of the guide jig, considerable time is required for implanting the metal elements in the synthetic resin body. Further, the ultrasonic energy transmitted through the metal elements to their mounting portions causes scarring or erosion of the guide bore surfaces due to contact of the latter with the metal elements with the result that the useful life of the guide jig is relatively short. It is also found that the metal elements, when implanted at their mounting portions in the synthetic resin body, are not in precise axial alignment with the respective guide bores of the jig with the result that removal of the jig from the metal elements is made difficult.
In order to avoid the foregoing disadvantages encountered in the use of ultrasonic energy for implanting the mounting portions of metal elements in the synthetic resin body, it has been proposed to dispense with the guide jig and to provide each of the metal elements with a guiding extension of reduced cross-section extending from the mounting portion so as to be initially received in the respective hole of the resin body for guiding the metal element during the movement of the mounting portion into such hole in response to the ultrasonic energy and axial pressure applied to the metal element as its free end, as in the first described method. However, such guiding extensions do not adequately guide the metal elements during the implanting of their mounting portions in the resin body with the result that the axes of the metal elements may deviate substantially from the desired normal relation to the surface of the body from which they project. Further, after the mounting portions of the metal elements are implanted in the resin body, the guiding extensions project from the holes at the underside of the body, that is, at the surface of the body opposed to that from which the metal elements project. Such projecting guiding elements are a nuisance in that they may interfere with the full utilization of the space under the resin body, particularly when the latter is the chassis or deck of a tape recorder or the like.